The conventional practice for constructing underground structures such as basements has been to excavate the ground, erect formwork, pour concrete and backfill.
This method requires use of earth-retaining sheathing to prevent the ground from collapsing and necessitates laborious tasks of erecting formwork, pouring concrete, removing the formwork after the concrete has hardened and backfilling the soil.
An object of this invention is to permit precise construction of underground structures with smooth wall surfaces by using simple equipment.